Galaxy Tab 7 copying using usb problem

[Dina Maged]

At first i was able to copy from PC to tab and vice versa using usb no problems but then 2 days ago when i tried copying it starts coping but then suddenly when it's almost about 80% or something it stops copying the file is there but of course it's corrupted, i tried with both the sd card and internal memory it's the same problem.